In order to counter problems of that kind, it is therefore known, during molding operations, to make use of cores that are soluble in water for some other liquid. In order to obtain sufficient solubility together with low density, the materials from which these mold cores are made are generally open-celled materials of the Aquacore™ kind (e.g. U.S. Pat. No. 6,828,373, EP 1745908 or EP 1695805). Such mold cores that are soluble in a liquid are themselves known.
Mold cores made in this way need to be sealed with a suitable material to prevent the material for constituting the future part that is to be molded, such as a resin or a metal in molten form from infiltrating into said cores. By way of example, sealing materials are described for example in documents DE 10 2005 011 930, DE 10 2005 011 488 or DE 10 2004 009 744.
The sealing material also makes it possible to ensure that the material constituting the parts obtained by molding, or portions of said parts, not contaminated by a material constituting the mold core.
The major drawback of mold cores of that kind is that, when fabricating them, it is necessary to have recourse to two groups of distinct materials, one for fabricating the cores and the other for sealing said cores. Those distinct materials are used during successive and different stages during the fabrication of sealed mold cores. That increases the number of materials to be managed and used, and also the number of fabrication steps of producing sealed mold cores. That inevitably leads to higher fabrication costs for such mold cores.
Another drawback is that the known sealing build-up (for instance one single layer upon the core) is very susceptible to damage. When damaged, the core can be infiltrated and the part to be built most likely a waste part.
Additionally, in many cases of sealing techniques, the sealing of complex shapes of cores cannot be achieved e.g. when using plastic films for sealing.